Copper-oxide rectifier



June 24, 1930. J SLEPIAN 1,765,502

COPPER OXIDE RECTIFIER Filed April 2, 1927 INVENTOR Jose 0h S/ep [an z 2 a AT:I'ORNEY Patented June 24, 1930 UNITED STATES PATENT OFFICE- J'OSEPH SLEIIAN, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR '10 WESTINGHOUSE ELEUIRIC 86 MANUFACTURING COMPANY, A CORPOBA EION OF ZEENNSYLVANIA COPPER-OXIDE REG'EEIER Application filed. April 2,

My invention relates to the general class of rectifiers which utilize the asymetrical current-carrying qualities of the junction between a metal and a compound thereof, such a as an oxide or a sulphide. More particularly,

my invention relates to copper-oxide rectitiers.

@no object of my invention is to provide methods and means for obtaining a good eleciotrical contact between a terminal member l conductor which is fragile and likely to be ill seamed with cracks and perforations and which covers-a base comprising a relatively good electrical conductor.

Other objectsof my invention will become apparent through reading the followin description taken in connection with the raw ings, in which;

Figure l is a sectional view of a copperoxide rectifier disc provided with a contact embodying my invention and Fig. 2 is a detailed sectional view, on enlarged scale, employed in the description of my invention,

To illustrate my invention by means of specific example, it may be applied to a copper-oxide rectifier formedin the following manner. A clean copper blank 1 which may, for example, be in the form of a circular washer, is heated in air or an atmosphere containing oxygen to produce an oxide coating 2 thereon, the temperature of the heat treatment being between about 500 C. and the melting point of copper, depending upon the exact method of preparation being utilized. Heating to lower temperatures is, however, within the scope of my invention. The heat treatment causes the oxidation of the mother copper and is believed to produce principally a layer of the red oxide of copper, 1. e., cuprous oxide,

although there may b L 1927. Serial in. 180,629.

by some means for another terminal upon the oxidized copper surface, the resulting unit possesses a unilateral electrical conductivity in respect to currents flowing from terminal to terminal and hence normally to the oxidized layer aforesaid.

For the commercial application of such a unilateral electrical conductor, it is desirable that the second mentioned contact, i. e., that of a line terminal to the outer oxide layer, shall be of relatively low electrical resistance. ll havefound that it is possible to obtain such a contact in the manner now about to be described.

According to one method of procedure, it first warm the oxidized copper surface to a temperature slightly above-the melting point of paraffin and then coat the surface with that substance. Having allowed the paraffin to solidify, 1' then rub the surface with fiocculent graphite until a good coating 3 is obtained thereon. By placing terminal plates 4 of sheet lead or other suitable metal in contact with this graphitized surface, l obtained a contact which has proved very satisfactory in practice,

While l do not wish to be limited to the consequences of a theory, it is my belief that the parafin fills numerous small cracks and perforations, which otherwise would exist in the oxidized layer, and thereby prevents the graphite from filling such cracks and making contact with the underlying mother copper, thereby partially short-circuiting the oxidized layer which is the efiective agent in producing the unilateral conductivity above described.

As an alternative method of making a satisfactory contact to the surface oxide, I may smear that surface with a thin coating of one of the condensation products of phenol and formaldehyde. Many condensation products .ties,,might be substituted for the materials l. have described.

While I have described the use aspir -no and phenol condensates as coatmg materials,

it will be noted that the properties which I desire in the substances to be used for this purpose are those of being an insulating material which may be applied in liquid form and later solidified. I, therefore, believe that many other materials, the identity of which will he evident to persons of skill in the arts, which possess the above-mentioned proper particular For example, it is my belief'that the condensation products of glycerine and phthalicanhydride would he useful for this purpose.

in the foregoing description, have referred to the layer of oxide on the copper as cuprous oxide and to the outer skin of black oxide, when present, as cupric oxide. In so employing these terms, I do not mean to specify that either layer is a pure homogeneous compound or that these terms represent its precise chemical composition.

lit will also be evident that, while l have described my processes of making electrical contacts in connection with their application to copper-oxide rectifiers, their field of use fulness is by no means limited to that particular application. The methods which l have described may be found useful in connection with making contact to many varieties of substances. They are well adapted to producing good electrical contacts to surfaces of fragile character and poor inherent electrical conductivity.

Although I have described my processes in a preferred embodiment, it is to be understood that they are not to be limited thereto, IS many changes and modifications will readily suggest themselves to the skilled workers in the art. I desire, therefore, that the appended claims shall be given the broadest interpretation consistent with their terms and with the state of the prior art.

I claim as my invention:

1. A rectifying unit comprising oxidized copper having a portion of its surface covered with a layer comprising an electrical insulator having the properties of changing from the liquid to the solid form without change of chemical composition and a layer roduct and a ood electrical conductor.

comprising a good electrical conductor.

2. A rectifying unit comprising oxidized copper having a portion of its surface covered with a layer comprising a phenolic condensation product and a good electrical conductor.

3. A rectifying unit comprising oxidized copper having a portion of its surface covered with a layer comprising a phenolic condensation product and graphite.

4i. A rectifying unit comprising a layer of mothercopper having an oxidized surface thereon and a coating for said oxidized surface comprising a phenolic condensation 5. A. rectifying unit comprising a layer of mother copper having an oxidized surface thereon and a coating for said oxidized surface comprising a phenolic condensation product and graphite.

(d. A rectifying unit comprising a layer of mother copper having oxidized surface thereon, a coating for said. oxidized surface comprising a phenolic condensation product and a good electrical conductor and a metallic terminal plate contact with said coating. I

7. A rectifying unit comprising a layer of mother copper having oxidized surface thereon, coating for said oxidized surface comprising a phenolic condensation product and metallic terminal plate in contact with said lay r. i

8. The method of making good electrical contact to a relatively poor conducting surface which comprises coating said surface h with a layer of a phenolic condensation prodnot and impregnating said coating with a layer of a conducting material.

9. The method of making good electrical contact to a relatively poor conducting surface superposed on a base which is a relatively good conductor which comprises coating said surface with a layer of a phenolic condensation product and impregnating said layer with conducting material.

10. The method of producing a conductor possessing a unilateral conductivity which comprises oxidizing a copper blank, removing the oxide from a portion thereof, coating another portion with a phenolic condensation product, impregnating said coated surface with powdered graphite, superposing a conducting plate on said graphitized surface and hardening said condensation product.

11. The method of producing a conductor possessing a unilateral conductivity which comprises heating a copper blank in air to a temperature substantially above 500 0., cooling said blank, removing the oxide from a portion thereof, coat-ing another portion with a liquid insulator adapted to exist as a solid, at a room temperature, and impregnating igidalcoating surface with a conducting ma- 12. The method of making good electrical contact to a relatively poor conducting surface which comprises coating said surface with a thin layer of a substance which can change from the liquid to the solid state without losing its insulating properties and cover-v ing said layer while still liquid with a layer of conducting material '13. The method of making good electrical contact to a relatively poor conducting surface which comprises coating said surface with a layer of phenolic condensation roduct, impregnating a portion of said ayer with graphite, pressing a terminal plate upon said surface and solidifying said condensation product by heating.

14;. The method of making good electrical contact to oxidized conducting surface whichv 7 comprises coating said surface with a layer of phenolic condensation product, impregnating a portion of said layer with graphite, superposing a terminal upon said graphite and solidifying said condensation product by heating.

15. The method of making a conductor possessing a unilateral conductivity which comprises oxidizing a copper blank, remov-' ing the oxide from a portion thereof, coating another portion with a phenolic condensation product, covering said coating with graphite superposing a metallic terminal upon'said graphited surface and solidifying said con-.

densating product by heating.

16. A rectifier unit'comprising an electricially conducting plate which has its surface coated with material that is a poor electrical conductor, said materal being coated with a layer comprising an electrical insulator having the properties of changing from the liquid to the solid form without loss of its insulating properties, and a coating of material which is a good electrical conductor covering said insulating material;

17. A rectifier unit comprisng an electrically conducting plate which has its surface coated with material that is. a poor electrical conductor, said material being of such a characterthat it contains interstices reaching from the outer surface of the material to the surface of said conducting plate an insulating material located withm said interstices,

and a coating of finel which is, a good electrical conductor dis? tributed over the surface of said first-named material divided material In testimony whereof, I-have hereunto subscribed my' name this 28th day ofjhlarch, 1927.

, JOSEPH sLEPmn; 

